The present invention relates to trucks configured to haul materials. More particularly, the present invention relates to trucks having a lift axle system configured to control the raising and lowering of lift axles.
Many trucks, such as dump trucks, are configured to haul large volumes of material, such as sand, gravel, asphalt, or earth. When loaded with such materials, the overall weight of the vehicles increases significantly. To prevent the weight per/axle ratio from exceeding state regulations, some trucks are provided with an additional axle or axles.
With each additional axle added to such trucks, the operating cost of each truck increases. The overall fuel economy of the trucks decreases because of extra drag and friction caused by the additional axle(s). Furthermore, replacement of the additional tires of the additional axle(s) raises the maintenance costs of each truck.
To lower the operating costs, some trucks are provided with lift axles that are lowered when the truck is loaded and lifted when the truck is not loaded. When lowered, the lift axle supports a portion of the overall vehicle weight and reduces the weight per/axle ratio. When the lift axle is lifted, the tires of the lift axle are not wearing or creating fuel economy-lowering drag on the truck. Thus, by raising the lift axle when not needed, tire wear is reduced and the fuel economy of the truck is raised and the overall cost of operating the truck is reduced.
According to the present invention, a lift axle control system is provided for a vehicle having a forward condition providing forward movement of the vehicle and a reverse condition providing reverse movement of the vehicle. The vehicle includes a chassis, a plurality of fixed axles supporting the chassis and having wheels normally in contact with the ground, a lift axle having wheels movable between a lifted position and a lowered position supporting the chassis, a lift axle mover configured to move the wheels of the lift axle between the lifted and lowered positions, and a source of pressurized fluid. The lift axle control system includes a housing, a control valve, and a switch. The control valve is configured to move between a lift position permitting the lift axle mover to move the wheels of the lift axle to the lifted position and a lower position controlling the flow of fluid between the source of pressurized fluid and the lift axle mover to move the wheels of the lift axle to the lowered position. The switch is configured to move between a lift position controlling movement of the control valve to the lift position and a lower position controlling movement of the control valve to the lower position. The switch is configured to automatically move to the lift position when the vehicle is in the reverse condition. The switch is also configured to automatically move to the lower position when the vehicle is out of the reverse condition.
According to another embodiment of the invention, a vehicle is provided that is configured to transport objects. The vehicle includes a chassis, a plurality of fixed axles having wheels normally in contact with the ground to support the chassis and permit movement of the chassis in forward and reverse directions, a vehicle direction controller configured to move between a drive position permitting movement of the chassis in the forward direction and a reverse position permitting movement of the chassis in the reverse direction, a lift axle having wheels movable between a lifted position spaced apart from the ground and a lowered position supporting the chassis, and a lift axle mover configured to move the lift axle between the lifted and lowered positions. The lift axle mover is configured to automatically lower the lift axle upon movement of the vehicle direction controller from the reverse position.
According to another embodiment of the invention, a lift axle control system for a vehicle is provided. The vehicle has a forward condition providing forward movement of the vehicle and a reverse condition providing reverse movement of the vehicle. The vehicle further includes a chassis, a plurality of fixed axles supporting the chassis and having wheels normally in contact with the ground, a lift axle having wheels movable between a lifted position and a lowered position supporting the chassis, a lift axle mover configured to move the wheels of the lift axle between the lifted and lowered positions, and a source of pressurized fluid. The lift axle control system includes a housing, a control valve coupled to the housing, and a pressure regulator. The control valve is configured to move between a lift position permitting the lift axle mover to move the wheels of the lift axle to the lifted position and a lower position controlling the flow of fluid between the source of pressurized fluid and the lift axle mover to move the wheels of the lift axle to the lowered position. The pressure regulator is coupled to the housing to control the pressure level of the fluid provided to the lift axle mover from the source of pressurized fluid.
According to another alternative embodiment of the present invention, a lift axle control system for a vehicle is provided. The vehicle has a forward condition providing forward movement of the vehicle and a reverse condition providing reverse movement of the vehicle. The vehicle further includes a chassis, a plurality of fixed axles supporting the chassis and having wheels normally in contact with the ground, a lift axle having wheels movable between a lifted position and a lowered position supporting the chassis, a lift axle mover configured to move the wheels of the lift axle between the lifted and lowered positions, and a source of pressurized fluid. The lift axle control system includes a housing, a control valve coupled to the housing, and a first pilot valve. The control valve is configured to move between a lift position controlling the flow of fluid from the source of pressurized fluid to the lift axle mover to move the wheels of the lift axle to the lifted position and a lower position controlling the flow of fluid from the source of pressurized fluid to the lift axle mover to move the wheels of the lift axle to the lowered position. The first pilot valve is coupled to the housing and configured to control movement of the control valve between the lift and lower positions.
According to another embodiment of the present invention, a lift axle control system is provided that is configured to control raising and lowering of a lift axle of a vehicle. The vehicle includes a lift bag positioned to raise the lift axle, a lower bag configured to lower the lift axle, and a source of pressurized fluid. The lift axle control system includes a housing and a control valve. The housing includes a lift bag port in fluid communication with the lift bag, a lower bag port in fluid communication with the lower bag, and a source port in fluid communication with the source of pressurized fluid. The control valve is configured to control the flow of fluid from the source of pressurized fluid to the lift and lower bags of the vehicle. The control valve is configured to automatically move to a lift position providing fluid from the source of pressurized fluid to the lift bag and exhausting the lower bag when the vehicle is placed in reverse. The valve is configured to automatically move to a lower position providing fluid from the source of pressurized fluid to the lower bag and exhausting the lift bag when the vehicle is taken out of reverse.
Additional features of the disclosure will become apparent to those skilled in the art upon consideration of the following detailed description when taken in conjunction with the accompanying drawings.